Field of the Invention:
The invention relates to a stripline laser.
Stripline or slab lasers are disclosed, for example, in U.S. Pat. No. 4,719,639 and U.S. Pat. No. 5,048,048. In the case of those lasers, an elongate narrow parallelepipedal discharge chamber for a gas, in particular CO.sub.2, is formed between planar electrodes which are parallel to one another. The gas is electrically excited by a radiofrequency voltage applied to the electrodes. In order to achieve a laser effect, resonator mirrors are disposed opposite rectangular end surfaces of the discharge chamber. Those resonator mirrors form a resonator only in a plane which is parallel to the electrodes, that is to say in the direction of the width of the discharge chamber. Transversely thereto, that is to say in the direction of the distance between the electrodes or the height of the discharge chamber, the two electrodes behave as waveguides.
U.S. Pat. No. 4,719,639 explains in further detail that both stable and unstable resonators are suitable. In particular, an unstable confocal resonator of the negative branch is proposed in U.S. Pat. No. 5,048,048.
Unstable resonators have a number of advantages which are important for high-power lasers, in particular. Thus, with unstable resonators it is possible, for example, to achieve high mode volumes and better utilization of the total volume region of the discharge chamber, that is to say of the entire excited gas, even in relatively short resonators. Compact high-power lasers can thus be built with the aid of unstable resonators.
However, unstable resonators have the property that the intensity distribution in the cross-section of the laser beam differs in the near-field and far-field range and that the far-field distribution moreover has, as a rule, secondary maxima which have to be filtered out by suitable devices.